The fire had been burning as planned for several hours until an unpredictable fire whirl, or dust devil, picked up burning ash and carried material outside of the planned burn area into high grass. Pushed by strong westerly winds, the fire quickly moved beyond containment efforts.

It was designated a wildfire at 1:30pm.

Some 70 firefighters are working the blaze, including trucks and crews from other agencies as well as two South Dakota Air National Guard Blackhawk helicopters and a Single Engine Air Tanker.

So far the fire remains within the park boundary and is burning land known as the “keyhole,” which was acquired in 2011. The visitors center is not threatened.